Communication Apparatus, and Method and Program for Controlling Same

1. A communication apparatus comprising: a communication unit configured to communicate by switching between a first communication period in which contention access control is performed and a second communication period in which non-contention access control is performed, wherein a first frequency bandwidth is used for a respective communication in the first communication period and the second communication period; a determination unit configured to determine the state of access contention in the first communication period; a first changing unit configured to change a frequency bandwidth used for communication in the second communication period and not to change a frequency bandwidth used for communication in the first communication period in case that the first communication period is shorter than the second communication period and access contention exceeding a predefined threshold has occurred in the first communication period, or to change the frequency band used for the communication of the first communication period and not to change the frequency band used for the communication of the second communication period in case that the first communication period is longer than the second communication period and access contention exceeding a predefined threshold has occurred in the first communication period; and a second changing unit configured to change a length of a communication period, which is either the first communication period or the second communication period and for which the frequency bandwidth has been changed by said first changing unit, from the length of the communication period used prior to changing the frequency bandwidth.

2. The apparatus according to claim 1 , wherein said first changing unit increases the frequency bandwidth used for the communication of the first or second communication period.

3. The apparatus according to claim 2 , wherein said second changing unit shortens the length of the communication period from the length of the communication period before changing the frequency bandwidth, wherein the frequency bandwidth used for the communication period is increased by said first changing unit.

4. The apparatus according to claim 1 , wherein said first changing unit changes the frequency bandwidth of the first or second communication period in accordance with length of the first or second communication period.

5. The apparatus according to claim 1 , wherein said determination unit determines the state of access contention of another communication apparatus that communicates via the apparatus of claim 1 .

6. The apparatus according to claim 1 , wherein this apparatus is a base station.

7. The apparatus according to claim 1 , wherein said determination unit determines the state of access contention for every type of data.

8. A method of controlling a communication apparatus for communicating by switching between a first communication period in which contention access control is performed and a second communication period in which non-contention access control is performed, wherein a first frequency bandwidth is used for a respective communication in the first communication period and the second communication period, the method comprising the steps of: determining the state of access contention in the first communication period; changing a frequency bandwidth used for communication in the second communication period and not changing a frequency bandwidth used for communication in the first communication period in case that the first communication period is shorter than the second communication period and access contention exceeding a predefined threshold has occurred in the first communication period, or changing the frequency band used for the communication of the first communication period and not changing the frequency band used for the communication of the second communication period in case that the first communication period is longer than the second communication period and access contention exceeding a predefined threshold has occurred in the first communication period; and changing a length of a communication period, which is the first or second communication period and for which the frequency bandwidth has been changed by said first changing unit, from the length of the communication period used prior to changing the frequency bandwidth.

9. A non-transitory medium encoded with a program for causing a computer, which is incorporated within a communication apparatus for communicating by switching between a first communication period in which contention access control is performed and a second communication period in which non-contention access control is performed, wherein a first frequency bandwidth is used for a respective communication in the first communication period and the second communication period, to function as: a determination unit configured to determine the state of access contention in the first communication period; a first changing unit configured to change a frequency bandwidth used for communication in the second communication period and not to change a frequency bandwidth used for communication in the first communication period in case that the first communication period is shorter than the second communication period and access contention exceeding a predefined threshold has occurred in the first communication period, or to change the frequency band used for the communication of the first communication period and not to change the frequency band used for the communication of the second communication period in case that the first communication period is longer than the second communication period and access contention exceeding a predefined threshold has occurred in the first communication period; and a second changing unit configured to change a length of a communication period, which is the first or second communication period and for which the frequency bandwidth has been changed by said first changing unit, from the length of the communication period used prior to changing the frequency bandwidth.

10. The apparatus according to claim 1 , wherein said determination unit determines the state of access contention in the first communication period in accordance with data transmission waiting time or occurrence frequency of data transmission wait in the first communication period.

11. The apparatus according to claim 1 , wherein said second changing unit changes lengths of the first communication period and the second communication period from that before changing the frequency bandwidths.

12. The apparatus according to claim 1 , wherein said second changing unit changes a ratio of the communication periods between the first communication period and the second communication period from that before changing the frequency bandwidths.

13. The apparatus according to claim 12 , wherein said second changing unit changes the ratio of the communication periods between the first communication period and the second communication period so that the total length of the first communication period and the second communication period is maintained even after changing the frequency bandwidth.

14. The apparatus according to claim 1 , wherein said communication unit performs wireless communication.